The proposed Program Project brings together the investigative activity of seven Faculty Members of the University of Chicago, who, already collaborating with each other because of common scientific interest, have now jointly planned a program directed at elucidating the structure-function relationships in serum lipoproteins and extending this information to the analysis of the mechanisms regulating the interaction of these lipoproteins with the cell membranes. The studies will be conducted in man and dogs utilizing serum lipoproteins separated by ultracentrifugation and cells obtained whether in culture (LM cells and skin fibroblasts) or from circulating blood (white blood cells). The studies will attempt to promote information at the molecular level on the mode of interaction of lipids with the serum lipoprotein apoproteins, on the mechanism of exchange of lipids between serum lipoproteins and model liposomes, and on the nature of the primary interaction between serum lipoproteins and cell surfaces particularly directing attention to isolated cell membranes with the ultimate goal of establishing the role played by circulating lipoproteins in cell function. Initially the work will be directed at defining normal parameters. Once these are established, the work will be extended to the analysis of lipoprotein disorders in man and experimentally induced hyperlipidemia in the dog. The planned studies are believed to be relevant to the problem of lipid transport in general and to atherosclerosis.